NOVEMBER 1999

Bird points to top of magnet where experiments will be lowered into the bore, or center.

FSU's new magnet is biggest ever

By Amy Olk
Special to the Florida State Times

What's 22 feet tall, weighs 34 tons and has world-wide attention?
It's not Godzilla. It's a monster-sized magnet, the latest addition to FSU's Magnet Lab.
Called the "45-T Hybrid," the $14-million magnet is a combination of two types of magnet designs which, when fully operational, will together generate a world-record DC magnetic field of at least 45 tesla (T) - the standard measure of the strength of a magnetic field.

Everyone knows how useful magnets are for attaching shopping lists to the refrigerator. Less well known is the role that magnets have played in the research that gives us electric lights, plastics, motors, computers, high-speed trains, semiconductors and MRI machines.
The new 45-T Hybrid will provide researchers from all over the world with a powerful new tool for studying the properties of matter -the building blocks of technology - at the molecular level.

"There's enormous interest in that magnet," says Janet Patten, director of governmental and public relations for the Magnet Lab.

"Experimental scientists are routinely doing research now at fields of 30 and 33 tesla (the previous world record, also held by the Magnet Lab), but to go from 33 to 45 - that just blows them away. Every time you make an incremental increase like we did from 30 to 33, that's a huge jump - although to the ordinary person, that might not seem like much."
So what is a tesla?

The strength of a magnetic field is measured in tesla and gauss: One tesla equals 10,000 gauss. At sea level, the earth generates a magnetic field of about 1/2 gauss, or 1/20,000 of a tesla. So how does a 45 tesla magnet compare to a refrigerator magnet?

John Miller, project leader for the 45-T Hybrid, allows the comparison, but warns that the comparative strength of magnetic fields cannot be conceived of in linear terms: A 2-T magnet is not simply two times stronger than a 1-T magnet.
Miller explains, "The energy required to create a given field is proportional to the square of the field multiplied by the volume containing the field."
He quickly does the math, based on the field of a very strong refrigerator magnet (1/10 of a tesla) and that of the 45-T Hybrid. The result?

"The Hybrid is really almost 8 trillion times stronger than a very strong refrigerator magnet," says Miller.

And the Hybrid is a different kind of magnet. There are basically two types: permanent magnets and electromagnets. Permanent magnets include refrigerator magnets, bar magnets and the magnets you find in games.

And whereas permanent magnets have a constant magnetic field, electromagnets, which derive their magnetic field from an electric current, can be turned on and off. Common examples of electromagnets are the solenoids in an automobile, magnetic door locks or the magnets used in junkyards to pick up cars and refrigerators - which might go as high as half a tesla.
All the magnets built at the Magnet Lab are electromagnets.

The 45-T Hybrid itself is made up of two types of electromagnets: a resistive electromagnet ("resistive" meaning that the metals the magnet is made up of have electrical resistance, thus requiring voltage, or power) and a superconducting magnet that has no resistance and requires virtually no power once it's running.

The Hybrid is a cylinder seven feet in diameter, with the resistive magnet in the center and the superconducting magnet forming the outside layer, or "outsert." When the Hybrid is turned on, the intense magnetic field is concentrated in a small hole, called a bore, in the center of the magnet. The bore is 32 mm (an inch and an eighth) wide - a tiny space in a giant mass of metal.
Dr. James Brooks, a professor of physics at FSU, is hoping to be one of the first to try out the Hybrid once it's in full operation.

In anticipation of the magnet's completion in October, he and a team of students prepared an experiment with four tiny samples of matter, all of which fit within one square centimeter (less than half an inch).

"It reminds me a little bit of the kids waiting for the new Star Wars film," says Brooks. "We feel like we've been camping outside the 'Hybrid Theater' for months with our experiments in hand."
The samples, which are composed of different types of layered matter, include superconducting materials, rare earth compounds and organic matter. They will be attached with fine wires to the tip of a six-foot-long stainless steel probe, encased in a special thermos, and inserted into the magnet's bore.

The wires run up through the probe to sophisticated volt meters, which are connected to a computer. As the samples are subjected to the 45-T magnetic field, Brooks and his students will be able to read the data on the computer screen as it evolves.
When subjected to the magnetic field, the motion of the electrons in the samples of matter will become quantized, meaning that the electrons in the layers will begin to move in circles.
"When the electrons start moving in these very tight orbits, they can interact with each other," says Brooks. "This shows up as special signals on the computer screen, involving what we call 'wiggles.' We can take those patterns and fit them to theoretical expressions - theory - and that tells us what's going on at the electron level."

Such experiments add to scientists' knowledge of the behavior of matter on the atomic scale, which can lead to many practical applications. The materials Brooks and his students are studying are candidates for new electronic and magnetic devices, such as sensors and memory storage devices.

Brooks waxes poetic when he speaks of the power of a 45 tesla magnetic field.
"We've run all kinds of interesting experiments in fields up to 33 tesla," he says. "But there are a lot of phenomena that we know (occur) above 33 tesla, and we just know it will be exciting. It will be like walking into a new forest or a new continent - you know there are new trees and rivers and new animals - but you have no idea how it's going to look."
Brooks and his students will enjoy the Hybrid's novel, user-friendly design that gives them more direct access to their work.

Hybrid magnets have traditionally been built with their controls on top, cluttering the space around the bore and making it difficult to install and monitor experiments. Mark Bird, an associate scholar/scientist with the Magnet Lab, points toward the magnet's top, which looks like a shiny, silver disk with a small hole in the middle.

"You see, the top of the magnet's flat - there are no obstacles here. There will be a deck put down ... so that people will be able to just walk up and install their experiments."
The controls (cryostats), which monitor vital signs like the temperature of the liquid helium used to keep the superconducting magnet at a super-frigid -459 degrees Fahrenheit, are conveniently placed to the side.

Because the Hybrid requires so much power, it will be the only magnet running when it is in use. Operating costs are always a concern when building a new magnet - the Magnet Lab already pays an annual electric bill of about $2.7 million, nearly 60 percent of which goes toward powering the lab's seven resistive magnets.

"As we design the next generation of hybrid magnets for this laboratory, we will be taking (the issue of cost) very seriously," Miller says. "The present plan is to demonstrate that hybrids can serve today's typical user . . . with all the flexibility and ease of use of present day resistive magnets, while requiring only about 1/3 the power and tying up only a single module of the laboratory's DC power supply."

Because superconducting magnets consume virtually no power, combining superconducting materials with traditional resistive technology, as was done with the Hybrid, is one way to reduce operational costs. However, superconducting magnets are much more expensive to build. (There are also intrinsic limits to how high a magnetic field they can reach before they stop superconducting).

As Bird puts it, "If you're sure you'll be able to get the operating money, but you're not sure you can get the capital money, you might put as much as you can into the resistive part. As far as a purely technical approach (to building a hybrid magnet) goes, people have different philosophies, but it basically comes down to how the funding works."
In the case of the 45-T Hybrid, a grant from the National Science Foundation supplied the $14 million needed to construct the magnet - $13 million of which was used to build the superconducting components.

Despite having set yet another world record with the 45-T Hybrid, researchers like Bird and Miller are not likely to be resting on their laurels in the face of ongoing, international competition to develop new and better technology for magnet-related research. As for the 45-T Hybrid, says Miller, "Its value will be extended. From the start, the superconducting outsert was designed to accept an insert capable of pushing the envelope to 50T."

However, he points out that building more powerful magnets in the future may require a whole new approach to magnet design.

If such change is to take place anywhere, the aptly named Innovation Park, where the Magnet Lab is located, seems a likely place for a revolution to begin.

The 330,000-square-foot Magnet Lab at FSU is the world's largest and highest-powered magnet laboratory, with a 40-million-watt power supply (10 percent of Tallahassee's total generating capacity). It is the main complex of the National High Magnetic Field Laboratory (NHMFL), a federal-state partnership supported by the National Science Foundation and the state of Florida and operated by FSU, the University of Florida and Los Alamos National Laboratory.
Each of the consortium partners offers unique research facilities, on a proposal review basis, to all researchers who wish to perform experiments in high magnetic fields. There is typically no charge for the use of the research facilities.

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